Phosphorus pentoxide in phosphoric



'of phosphorus pent-a in the production-of th Patented Sept. 12, 1950 PATENT OFFICE rnosriioaos IL'ENTOXIDE IN rnosrnomc eon) roa'rnro AN'rHoNE RING CLOSURE Wilhelm Schmidt-Nickels, Little York, N. J assi'gnor -t'0 G ci-1ral Aniline & Film Corporation, New.ilorkphl;Y.,'a. corporation of Delaware 'NoD'r'awing. .Application December I6, 1948,

. gserial No. 65,724

This invention relates to an improved process for cyclicizing an anthraquinone-thiophenyl ether containing a carboxylic acid group to the corresponding thioxanthone.

Heretofore, the formation of such thioxanthone ring systems was usually carried-out by the use oiide. IChe handling of causes great difficulties "compounds. Concentrated sulfuric acidcannot be used iorthe'serin phosphorus pentachlor Y 8 Claims. (01. 260-328) closures as "it gives undesirable sidefreactions,

quinone-thiophenyl ether containing a carboxylic acid group to the corresponding thioXanthone by the use of a reagent which is easy to handle.

7 It is a further objector the present invention to provide a new process to 'cyclicize an" 'anthraquinone-thiophenyl ether containing a carboxylic acid group to the corresponding thioxanthone in substantiallyquantitative yields.

These and other objects are attained by the present invention, wherein the cyclicization-of an anthraquinone-thiophen d' ether containing a carboxyiic acid. group to the cori'esponding thioxanthone is effected by the use of a solution of phosphorus pentoxideiin ph'osphor-ic acid preferably equal molar (142 parts of phosphorus pentoxide in 98 parts of phosphoric acid). In general, the reaction is carried out by heating the aforesaid carboxylic acid compound with the solution of phosphorus pentox ide in phosphoric acid to 100 to 210 C. Thereactio'n proceeds as follows:

X X l Y o s Z Z r205 H3PO4 X X l l i n t0 Joon Y i I wherein Rfifs hydrogen or. a halogen, i. e.-, chlorine, bromine, etc; X is hydrogen, halogen, or alkyl, i. e., methyl, ethyl, propyl, butyl, amyl, h'exyl, oct'yl, jdodecyLstea'ryl, etc.; alko'xy, i. e., methoxy, ethoxy, Dr GpOXyi, butyroxy, etc; or aryl oXy, i. e., phenoxy; Yis hydrogen, chloro, hydroxy or. amino; and one Z is hydrogen and the other is a carhoxylic acid "group.

The carboxylic' acid group may be either in the anthraquinone -s'ystezn orin the phenyl ringoi the thioether and is in ring: closure position, i. e, ortho to the thioethe'r bridge. The reaction with these "types at oinpounds may be illustrated as follows As indicated in the. general formula, reactive groups such as the N112 group halogen and the like are not aifeCt-edby the phosphorus pentoxidephosphoric acid.

As is evident the compounds, the ring closure of which is contemplated herein, are anthraquinone thiophenyl compounds bearing a carboxylic acid grouping in. orth-o positionto the sulfur bridge; said compounds hairingaireeposition ortho 'to said bridge in the ring system other than that containing the. carboXy group. Such compounds areembraced by the above general formula and are also illi1strated supra. Additional examples of I such compounds are:

anthraquin'onyl- 1 -thiosalicylic acid.

z-carboxy -anthraouinony1 2,5 d'ichlorobenzeneli-amino-anthraquinonyl=l -thio-5- (or 3-) chlorsalicylic acid- 5-amino-2% cariooXy anthra'quinonyl l-thiooenzene 'arithraquinonyl l=thi'o-3 inethy1 salicylic acid 2-carboxy-anthraquinonyl 4 bromo benzene-- thiol The following examples are illustrative of the present invention but are not to be construed as limiting the invention.

Example 1 Two hundred parts of anthraquinonyl-l-thiosalicylic acid (obtained from l-chloroanthraquinone and thiosalicylic acid) were introduced with stirring into 2000 parts of an equal molar solution of P205 in H3PO4. The mixture was heated up to 160 C. for 20 minutes. The mass was then poured into 20,000 parts water, stirred for hour, filtered and washed with water. The wet presscake was introduced into 5000 parts water, 135 parts by volume of 20% sodium hydroxide solution and 200 parts by volume of sodium hypochlorite solution. The suspension was boiled for hours while replacing the evaporated water from time to time. Finally the product was filtered, washed neutral and dried. Weight=169 partsi'z I The product can be recrystallized from nitrobenzene as follows: 160 parts of the above reaction product were introduced into 1200 parts by volume of nitrobenzene. When heated to 205 C. a clear solution was obtained. The

thioxanthone crystallized at room tempera ture. It was filtered, washed with nitrobenzene, then with alcohol and dried. Weight=l parts. Found: S=9.33%. Theory for C21H10O3SZ S=9.36%. The product dyed cotton orange from a violet vat.

Example 2 One hundred and seventy parts of the reaction product of 1-nitroanthraquinone-2-carboxylic acid and 2,5-dichlorobenzenethiol of the formula:

were introduced with stirring into 1700 parts of an equal molar solution of P205 in H3PO4. The mixture was heated to 180 C. and stirred at 180 C. for minutes. The charge was worked up as described in Example 1. The product was pure enough for all technical purposes without recrystallization. The weight obtained after: hypo bleaching was 144 parts. The product dyed cotton yellow from a violet vat.

Example 3 One hundred and seventy parts of the reaction product of 1-chlor-5-aminoanthraquinone and thiosalicylic acid were introduced with stirring into 1700 parts of an equal molar solution of P205 in H3PO4. The mixture was heated to,

4 200 C. and stirred at 200 C. for 20 minutes. The charge was worked up as described in Example 1. Weight obtained=159 parts.

The product is an intermediate for dyestufl syntheses. For most practical purposes it is pure enough without recrystallization or other purifications.

While the above examples are illustrative of the invention, modifications and variations will be apparent to those skilled in the art and are within the scope of the invention as defined by .the appended claims.

I claim:

1. A process for forming a thioxanthone from an anthraquinone-thiophenyl ether containing a carboxylic acid group in ortho position to the sulfur ether atom, which comprises reacting said acid with phosphorus pentoxide in phosphoric acid.

2. A process for forming a thioxanthone from an anthraquinone-thiophenyl ether containing a carboxylic acid group in ortho position to the sulfur ether atom, which comprises reacting said acid with an equal molar solution of phosphorus pentoxide in phosphoric acid.

3. A process for forming the corresponding thioxanthone from a compound of the following general formula:

X X I I I II I I ZZ R wherein R is selected from the group consisting of hydrogen and a halogen, X is selected from the group consisting of hydrogen, halogen, alkyl, alkoxy, and aryloxy, Y is selected from the group consisting of hydrogen and an amino group and one Z is hydrogen and the other Z is a carboxylic acid group; which comprises heating said compound in the presence of a. mixture of phosphorus pentoxide in phosphoric acid.

4. A process for forming:

which comprises heating:

coon

in the presence of a mixture of phosphorus pentoxide and phosphoric acid.

5. A process for forming:

which comprises heating:

COOH

in the presence of a mixture of phosphorus pentoxide and phosphoric acid.

6. A process for forming:

which comprises heating:

OOH

in the presence of a mixture of phosphorus pentoxide and phosphoric acid.

7. A process for forming:

NHa g which comprises heating:

(. ZOOH in the presence of a mixture of phosphorus pentoxide and phosphoric acid.

8. A process for forming a thioxanthone from i an anthraquinone-thiophenyl ether containing a carboxylic acid group in ortho position to the sulfur ether atom, which comprises mixing said acid with a mixture of phosphorus pentoxide in phosphoric acid, heating the mixture to a temperature in the range 100 to 210 C. and washing the product with water.

WILHELM SCHMIDT-NICKELS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,880,490 Rosch Oct. 4, 1932 FOREIGN PATENTS Number Country Date 402,741 France Sept. 7, 1909 OTHER REFERENCES Behr, Berichte, 7, 578579 (1875). 

1. A PROCESS FOR FORMING A THIOXANTHONE FROM AN ANTHRAQUINONE-THIOPHENYL ETHER CONTAINING A CARBOXYLIC ACID GROUP IN ORTHO POSITION TO THE SULFUR ETHER ATOM, WHICH COMPRISES REACTING SAID ACID WITH PHOSPHORUS PENTOXIDE IN PHOSPHORIC ACID. 